Role of adsorbed water in inducing electron accumulation in InN

Abstract

Nominally undoped indium nitride (InN) is known to have an electron accumulation layer on its surface, and prior studies have shown this layer to be sensitive to chemical species. However, the exact roles of these species and the underlying mechanism of e- accumulation layer formation are not clear. In this work, it is shown that ambient adsorbed water on the InN surface strongly enhances the e- accumulation layer formed due to intrinsic surface states. Desorption of ambient physisorbates leads to a decrease in band bending, an increase in work function in undoped InN, and the observation of a p-type Mott-Schottky behavior in Mg:doped InN. The underlying mechanism of this surface-adsorbed water interaction may be through a process called "surface transfer doping," which has previously been reported in hydrogenated diamond and other semiconductors such as GaN and ZnO.